The invention relates to electrical machines of the kind having a stator and a rotatable armature, the winding of which is energized via a commutator or via slip rings. Such electrical machines are widely used as motors or as generators.
It has been found that in such machines the commutation performance is impaired after a long period of operation. Especially in small motors it may happen that the brushes cooperating with the commutator become damaged or broken.
It is therefore an object of the invention to improve an electrical machine of the kind referred to such that the commutation performance is not impaired even after a long period of operation.
It is another object of the invention to provide an electrical machine in which the brushes do not become damaged due to a relative axial displacement between the commutator on the one hand and the brushes on the other hand.